The semiconductor industry has experienced exponential growth. Continuous advancements in lithographic resolution have paced uninterruptedly to support critical dimensions (CDs) of 90 nm to 65 nm, 45 nm, 32 nm, 22 nm, 16 nm and below. New techniques in lithography have been developed, such as immersion lithography, multiple patterning, extreme ultraviolet (EUV) lithography and e-beam lithography. The challenges being raised by new lithography techniques are not only in resolution but also in economy (e.g., cost of upgrading and loss of throughput). A lot of developments have focused on extending existing lithography techniques to the next technology generation.